1. Technical Field
Photoresist compositions are disclosed for top-surface imaging processes by silylation (TIPS). In particular, photoresist compositions are disclosed which are useful in TIPS, by crosslinking a protecting group of a cross-linker and a hydroxyl group of a photoresist polymer in an exposed region, and by reacting the hydroxyl group and a silylating agent in a non-exposed region.
2. Description of the Background Art
Recently, the chemical amplification of type DUV photoresists have been investigated in order to achieve high sensitivity in minute image formation processes for preparing semiconductor devices. In general, a useful photoresist for ArF, VUV, EUV and E-beam has a variety of desired characteristics, such as high transmissibility at the wavelength of each light source, high etching resistance, and high adhesiveness to a wafer. In addition, the photoresist should be easy to develop in readily available developing solutions, such as 2.38wt % and 2.6wt % aqueous tetramethylammonium hydroxide (TMAH) solutions.
Research has been performed on resins having a high transparency at a wavelength of 193 nm and dry etching resistance similar to Nobolac(trademark) resin. However, most of the photoresists are not suitable for VUV due to their poor transmittance at the 157 nm wavelength. While photoresists containing fluorine and silicon have good transmittance at these wavelengths, most photoresists containing fluorine with a polyethylene or polyacrylate polymer backbone have weak etching resistance, low solubility in an aqueous TMAH solution and poor adhesiveness to the silicon wafer. In addition, these photoresists are difficult to mass-produce and are expensive. Furthermore, during a post-exposure bake (PEB) process these photoresists can generate HF which can contaminate a lens or corrode a device. Thus, these photoresists are generally not suitable for commercial use. On the other hand, photoresists containing silicon should satisfy required silicon content (over 10%) in the etching step. For this, monomers comprising silicon are used in a large volume, which increases hydrophobicity of the photoresist. Therefore, the photoresist cannot satisfy selectivity between the exposed region and the non-exposed region in the aqueous TMAH solution, and, as a result, has low adhesiveness to the silicon wafer.
Some of the known limitations of the photolithography include substrate""s influence on light (e.g., reflection, scattering, diffraction, etc.), notching, standing wave effect, pattern collapse, non-uniformity of a critical dimension (CD), isolated and grouped bias (IG bias) and the like.
On the other hand, thin layer imaging technologies such as TIPS are effective patterning processes for photolithography using a wavelength below 193 nm and optical lithography using an extreme ultraviolet (EUV) wavelength (e.g., 13 nm).
In TIPS, a shallow exposure is performed which forms a latent image by diffusion of acids that are generated in the exposed region. The exposed region is then selectively silylated with a silylating agent. The silylated region serves as a mask, and the non-silylated region is dry-etched by O2 plasma. Thus, TIPS requires photoresist compositions having a high energy absorption coefficient and process conditions that have high selectivity in etching non-silylated regions during the O2 plasma treatment.
TIPS is rarely influenced by substrates and topology. In addition, TIPS is less sensitive to transparency, adhesiveness and etching selection ratio of the photoresist composition. TIPS also has a much wider depth of focus in high resolution than a single layer resist (SLR). Thus, in some aspects, TIPS has more advantages than a general resist patterning process.
In addition, as compared with a wet development of SLR, the dry development process of TIPS can be applied to a thick resist process in a high aspect ratio without causing a pattern to collapse. This advantage is useful on a substrate having a relatively low etching selection ratio, such as an oxide or metal. As a result, TIPS is recognized as an alternative to SLR.
The TIPS is essentially applied to the semiconductor device manufacturing process due to decreased geometry of the required resist pattern and increased necessity of a short wavelength in a lithography process. However, there are some problems in using TIPS for a high resolution photoresist pattern formation, such as lack of a high photosensitive photoresist and line edge roughness (LER) after dry etching process
Photoresist compositions are disclosed which are suitable for top-surface imaging process by silylation (TIPS) using a light source such as KrF (248 nm), ArF (193 nm), VUV (157 nm), EUV (13 nm) and E-beam.
Semiconductor elements produced by using the above photoresist composition are also disclosed.